Amino acids embrace many naturally occurring materials and as well many unnatural compounds which have high therapeutic utility. One amino acid which is especially useful as an antihypertensive agent is .alpha.-methyldopa, chemically identified as (S)-3-(3,4-dihydroxyphenyl)-2-methylalanine. While the compound has been administered orally as the acid salt, for certain applications the ester form is desirable. Ethyl ester of methyldopa hydrochloride is currently employed for intravenous application. In U.S. Pat. No. 3,983,138 there are disclosed esters and derivatives of .alpha.-methyldopa which are active in the treatment of hypertension, and it is further disclosed that some of these compounds have much higher activity than .alpha.-methyldopa itself. One of the esters described in the patent is especially useful, namely, the .alpha.-pivaloyloxyethyl ester and the preparation of said ester in good yields is especially desirable. U.S. Pat. No. 4,440,942 describes the preparation of a crystalline form of diastereomeric L-.alpha.-methyldopa POE ester by a reaction carried out in an atmosphere of nitrogen with the application of heat for an extended period. While this method is an improvement over earlier methods, a method which produces better yields and consistent good yields is still desired.